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Nickel-aluminides-reinforced nickel-matrix composites were fabricated from 0.05mm-thick nickel foils and 0.012mm-thick aluminum foils, in a process using a pulsed-current hot pressing (PCHP) equipment, and the effect of reaction temperature on mechanical properties of the composites was investigated. The composites were of laminated structure and composed of Ni and reacted layers containing Ni-aluminides. The chemical composition of the reacted layers was dependent on reaction temperature in the temperature range employed. Tensile testing at room temperature revealed that the reaction temperature evidently influences mechanical properties, including tensile strength, elongation and fracture mode, of the composites. The tensile strength and elongation of composites fabricated at 1373K were 500MPa and 3.8%, respectively. Microstructure observations of fractured specimens revealed that Ni layers of the composite played a significant role in prohibiting the growth of numerous cracks emanating from Ni-aluminides. In the case of composites fabricated at 1373K, in addition, crack propagation between Ni-rich Al-solid-solution layers and cellular Ni₃Al in the Ni-aluminides were prevented by mutual interaction.

By introducing ZrO₂ (4Y) powder into the thermit, Al₂O₃/ZrO₂ (4Y) composite ceramics of different composition and microstructures were prepared through combustion synthesis under high gravity, and the correlations of composition, microstructures and mechanical properties of composite ceramics were investigated. The results of XRD, SEM and EDS showed that Al₂O₃/33%ZrO₂ (4Y) were composed of random-orientated rod-shaped colonies consisting of a triangular dispersion of orderly submicron-nanometer t-ZrO₂ fibers, surrounded by inter-colony regions consisting of spherically-shaped micronmeter t-ZrO₂ grains; meanwhile, Al₂O₃/45%ZrO₂ (4Y) were comprised of spherically-shaped micron-meter t-ZrO₂ grains. Similar to the international directionally solidified Al₂O₃/ZrO₂ (Y₂O₃), the EDS results also indicated that there are no impurities, amorphous phases and grain boundaries but clean phase interfaces in two ceramic composites. Compared to the international directionally solidified Al₂O₃/ZrO₂ (Y₂O₃), the increase in hardness and flexural strength of Al₂O₃/33%ZrO₂ (4Y) in the experiment was due to small-size defect and high fracture toughness induced by compressive residual stress effect and transformation toughening mechanisms; meanwhile, high flexural strength of Al₂O₃/45%ZrO₂ (4Y) was considered to be a result of the fine spherically-shaped t-ZrO₂ grains separated from the melt under high gravity, and high fracture toughness induced by transformation toughening and micro-crack toughening mechanisms.

The effect of Al content on the self-propagating high-temperature synthesis (SHS) reaction among Al, TiO₂ and B₂O₃ was experimentally investigated. The Al content plays an important role in controlling the reaction behaviors. With the increase in reactant Al, the maximum combustion temperature decreases, the propagating wave velocity first increases and then decreases, while the ignition delay time shows an opposite tendency. More importantly, the increase of the Al content in the reactants has an insignificant effect on the phase constitutions of the synthesized products but reduces the size of the synthesized TiB₂ particles.

In this work, the in situ SiC/Al composites were successfully fabricated by the method of combustion synthesis and hot press consolidation in an Al-C-Si system. The effect of alloying elements (Mn, Zn, Ti) on the phase constitution and microstructure of in situ SiC/Al composites were investigated. Results indicated that the Al${}_{11}$Mn${}_{14}$ and Ti${}_x$Si${}_y$ phases were formed in the SiC/Al composites with the addition of Mn and Ti, respectively. By the addition of Mn, the size of the synthesized SiC particles was obviously reduced, and consequently the amount of SiC particles was increased. Meanwhile, the percentage of the submicro SiC particles increased about from 22% to 83%. However, the addition of Zn and Ti had little effect on the size of SiC particles.

The low ductility and insufficient strength of the TiAl alloy are still two major obstacles for its applications. It was demonstrated that Ti₅Si₃ could improve the ductility of TiAl alloy, while it can’t obviously improve the strength. In order to further improve the strength of Ti₅Si₃/TiAl composite to obtain TiAl materials with excellent strength and ductility, the effects of alloying elements (Cu, Zn, W and Mo) on the compression strength of the in-situ nano-Ti₅Si₃/TiAl composite were investigated in this work. With the addition of 2 at.% Me (Me $=$ Cu, Zn and W, respectively), the compression true yield strength (${\sigma }_{\mathrm{\text{true}}}^y$) of the composite increases from 613 MPa to 840, 660 and 706 MPa, respectively. Moreover, the addition of Zn results in the increase of the ${\sigma }_{\mathrm{\text{true}}}^y$ with no obvious sacrifice of ductility. Finally, the 4 vol.% nano-Ti₅Si₃/TiAl-2Zn composite obtained the best comprehensive properties. Compared with the TiAl alloy, the ${\sigma }_{\mathrm{\text{true}}}^y$, ${\sigma }_{\mathrm{\text{true}}}^{\mathrm{\text{UCS}}}$ and ${𝜀}_{\mathrm{\text{true}}}^f$ of the Ti₅Si₃/TiAl-2Zn composite increases by 195, 140 MPa and 2.6%, respectively.

Nanoparticles of samarium barium antimonate (Ba₂SmSbO₆), a complex perovskite has been synthesized using an auto-ignition combustion process for the first time. The nanoparticles thus obtained have been characterized using X-ray diffraction, thermo-gravimetric analysis, differential thermal analysis, Fourier transform infrared spectroscopy, scanning electron microscopy and transmission electron microscopy. The XRD studies have shown that the as-prepared powder is phase pure Ba₂SmSbO₆ and has a complex cubic perovskite (A₂BB'O₆) crystalline structure with lattice constant a = 8.491 Å. The particle size of the as-prepared powder was in the range 20–50 nm. The nano crystals of Ba₂SmSbO₆ synthesized by the combustion technique could be sintered to 97% of the theoretical density by heating at a temperature of 1550°C for 2 h. By the present combustion synthesis a phase pure Ba₂SmSbO₆ nanopowder could be obtained by a single step process without the need of any calcination step.

This study investigates the optical properties of samarium-doped microstructured and nanostructured CaO–CeO₂ mixed solutions. Conventional solid state method and auto-igniting combustion synthesis were used for the preparation of the samples. The as-prepared samples were characterized using X-ray diffraction, Fourier Transform Infrared spectroscopy, Transmission Electron Microscopy, UV-Visible spectroscopy and photoluminescence spectroscopy. A mixed phase formation with phases of CaO, CeO₂ and Ca(OH)₂ was observed form X-ray diffraction studies. The transmission electron microscopic studies have shown that the average particle size of the as-prepared powder was in the range of 30–40 nm. A blueshift is observed in the bandgap of the nanocrystalline samples. Strong orange–red emission was observed for Sm${}^{3+}$-doped samples and the chromaticity values were calculated using CIE chromaticity diagram.

Y³⁺ doped CeO₂ nanopowders (Ce_0.9Y_0.1O_1.95, abbreviated as YDC) were synthesized by citrate-nitrate-auto combustion process using cerium nitrate hexahydrate, yttrium nitrate hexahydrate and citric acid. The as-synthesized powders were calcined at 700°C and converted into dense bodies followed by sintering at 1200°C. The microstructure of the synthesized powders and sintered bodies were examined by scanning electron microscopy (SEM). The surface morphology of the nanoparticles and clusters were also analysed by transmission electron microscopy (TEM). The particles size of the YDC was found to be in the range from 10 to 30 nm, which is in good agreement with the crystallite size calculated from X-ray peak broadening method. Also, the X-ray diffraction confirmed that the Ce_0.9Y_0.1O_1.95 crystallizes as the cubic fluorite structure of pure ceria. The optical absorption by functional molecules, impurities and oxygen vacancies were analysed by FTIR and Raman spectroscopic studies. From the FTIR spectrum, the absorption peak found at 530 cm^-1 is attributed to the vibrations of metal-oxygen bonds. The characteristic Raman peak was found to be 468 cm^-1, and the minute absorption of oxygen vacancies were observed in the region 500–640 cm^-1.

Rare earth oxides are considered materials that are commonly used in high performance luminescent devices, magnets, catalysts and various other practical applications such, as electronics, magnetism, nuclear technology, optics and catalysis. Using ${\mathrm{\text{Gd}}}_2{\mathrm{\text{O}}}_3$ nanoparticles synthesised by combustion route and calcinated at various temperatures (600${}^{\circ }$C, 800${}^{\circ }$C, 1000${}^{\circ }$C, and 1200${}^{\circ }$C), we have investigated its phosphors nature in this study. We evaluated the phase purity and grain size distributions from the powder X-ray diffraction patterns of all the samples. This was done using the Rietveld refinement and the FW$\frac{1}{5}$/$\frac{4}{5}$M technique. Our observation of the ${\mathrm{\text{Gd}}}_2{\mathrm{\text{O}}}_3$ nanoparticles grain size distribution was made possible using transmission electron microscopy pictures and HRSEM images. The photoluminescence spectrum of ${\mathrm{\text{Gd}}}_2{\mathrm{\text{O}}}_3$ nanoparticles showed emission in the region near-band-edge blue and green emission. To detail the photoluminescence behavior, the excitation, emission spectra and CIE 1976 plot were recorded and the CIE coordinates were found to be $X=0.207$ as well as $Y=0.206$ that look like blue. The use of phosphors nature is enabled by studying the impact of grain size and the linear dependent behaviour of ${\mathrm{\text{Gd}}}_2{\mathrm{\text{O}}}_3$ nanoparticles.

Red-emitting Mn²⁺-doped AlN(AlN:Mn²⁺) phosphors were successfully prepared by a highly effective combustion synthesis method. The phase purity, morphology, element-composition and luminescence properties of the synthesized phosphors were investigated. X-ray diffraction (XRD) results show that the Mn²⁺-doped into the AlN host did not induce a second phase and distort the structure significantly. Scanning electron microscopy (SEM) images display that the phosphors have an irregular shape with a particle size in the range of 1–5 μm. X-ray photoelectron spectroscopy (XPS) spectrum indicates that Mn ions are divalent state. The synthesized AlN:Mn²⁺ phosphors exhibit a strong red emission centered at ~ 600 nm, which is ascribe to the ⁴T₁(⁴G)–⁶A₁(⁶S) transition of Mn²⁺ under ultraviolet excitation. The emission intensity reaches its maximum when Mn²⁺-doped concentration is 3 mol%.

Blue–green-emitting Y₂O₃ : $x$Bi${}^{3+}$ ($x$ = 0.25–1.50 mol.%) phosphors were synthesized by a solution combustion method followed by high temperature annealing. The effect of Bi${}^{3+}$ ion concentration on the crystal structure and photoluminescence performance of the phosphors were investigated. The results show that the cell parameter and cell volume of Y₂O₃host were increased with the Bi${}^{3+}$ concentration, and all the phosphor powders exhibited porous lamellar structure with the width of $\sim$500 nm. The emission spectra of the phosphors (${\lambda }_{ex}$ = 335 nm) consist of three broadband emission spectra centered at 370 nm (³A${}_u\to {}^1$A${}_g)$, 410 nm (³E${}_u\to {}^1$A${}_g)$ and 486 nm (³B $\to {}^1$A), respectively. The phosphor exhibited the optimal luminescence performance at $x$= 0.50% and the dipole–dipole and quadrupole–quadrupole interactions among Bi${}^{3+}$ ions could lead to the concentration quenching. The color coordinates of Y₂O₃:0.50%Bi${}^{3+}$ were (0.1595, 0.2250), indicating that the as-synthesized blue–green phosphors have a broad application prospect in the field of white light-emitting diodes.

In this paper, we report on the thermoluminescence response of nanocrystalline co-doped alkaline earth aluminates synthesized by combustion method using metal nitrate as precursor and urea as fuel. A broad TL glow peak was observed at 367 K with a shoulder at 400K. TL Anal program has been used for GCD curve fitting. The Kinetic parameters like, the activation energy (E_α), the frequency factor (s) and the order of kinetics were calculated for the SrAl₂O₄: Eu²⁺, Dy³⁺nanophosphors. The best dopants combination was Eu (1 mol%) and Dy (2 mol%). The samples were irradiated with γ-dose in the range 20Gy–800Gy, at room temperature. A shift from 367 K to 376 K was also observed in the main peak with an increase in irradiation dose which suggest that the irradiation doses affect the distributions of traps produced by the gamma-ray irradiations. Kinetic parameters also suggest that TL glow curve in SrAl₂O₄: Eu²⁺, Dy³⁺ nanophosphors is obeying second order kinetics. The nanophosphors show linear response with dose.

The following sections are included:

• Introduction

• Experimental Methods
  • Time Resolved Diffraction Measurements
  • Preparation of Combustion Synthesis Specimens
  • Temperature Profile Measurements
  • Spatially Resolved X-ray Diffraction (SRXRD) Measurements
  • Titanium Samples for Welding
  • Welding Setup and Procedure

• Results
  • Time Resolved Diffraction Data
    • The Synthesis of TaC
    • The Synthesis of Ta₂C
    • Temperature Profiles of the Combustion Front
  • Spatially Resolved X-ray Diffraction Data
    • Phase Mapping in the HAZ of Ti Fusion Welds
    • The α Pattern
    • The α_AR Pattern
    • The α_RG Pattern
    • The α_BT Pattern
    • The β Pattern

• Discussion
  • Combustion Reaction Temperature
  • Chemical Dynamics of the Ta-C Combustion Synthesis
  • Thermal Distribution in a Ti Fusion Weld
  • The α_AR Pattern: Location and Associated Microstructure
  • The α_RG Pattern: Location and Associated Microstructure
  • The β and β_L Pattern: Location and Associated Microstructure
  • The α_BT Pattern: Location and Associated Microstructure

• Concluding Remarks

• Acknowledgments

• References